Shaler.] 202 [January 19. 



merit of the bottom, at least, varying a good deal with the surface of 

 the country traversed. It is not necessary to assume that this move- 

 ment extended to any very great distance inland, as it has not been 

 proved that any boulders have been transported more than thirty 

 or forty miles along the direction of the strice. It is not possible 

 to deny that detrital matter may have been brought from greater 

 distances inland along this path, for the facts have not yet been care- 

 fully analyzed; but as yet I have been unable to find any masses 

 bedded in the drift which could be referred to more remote points, 

 while by far the greatest number are clearly traceable to rocks which 

 are found in the immediate vicinity of the point of deposit. 



2. The rending from the floor of the ice stream of large quantities 

 of fragments which were ground to mud in the jam of materials at 

 the base of the ice sheet, or lifted into the body of the mass by the 

 irregular tumbling movements which must have occurred in the pas- 

 sage of the stream over the broken surface it traversed, followed 

 by the melting of the glacial accumulation and the deposition of the 

 mass of detritus it contained in the unstratified shape in which we 

 now find its remains. 



3. The action of the drainage streams and tidal currents on this 

 incoherent mass, the former probably swollen for a time by the waters 

 of the melting ice, cutting away the incoherent mass of drift, and 

 clearing out the old channels in which they ran before the glacial 

 period, leaving drift ridges capping the sammits of the original, low, 

 rock hills of the country. 



4. During these actions, but at times which remain to be deter- 

 mined with exactness, certainly one, probably two movements of the 

 surface took place, which have left only an imperfect record ; the 

 first and well proven, being a submergence of at least one hundred 

 feet; for to that height on our hills of drift are superficial patches of 

 stratified materials found. This movement probably occurred at the 

 end of the ice time, and the change of shore did not last very long. 

 The other movement was a depression also; if it really occurred, it 

 happened at the close of the elevation which followed this first de- 

 pression, in which the land seems to have risen a little higher than it 

 is at present, the difference being probably not over twenty to forty 

 feet. I regard this second depression as probable, but not proven. 



The reader who is familiar with the disposition of the unstratified 

 drift on our shores, will recognize the fact that the mass is much greater 

 at some points than others. This is to be expected. If we examine 



